猕猴前额叶皮层神经元在视觉延缓分辨活动中的放电活动

在已学会颜色延缓分辨的3只猕猴上,用钨丝微电极记录前额叶背外侧部皮层神经元的放电活动,着重分析神经元放电活动与颜色延缓分辨活动的各个时期之间的相互关系。延缓分辨任务开始时,同时把红色光和绿色光分别投射在测试板上的两个显示窗上,约持续1.2s(暗示期)。颜色光熄灭后2—4s(此为延缓期),各自位于每一显示窗下的两个反应键同时向猴方推出。自此,反应期开始,动物应马上有选择地作出按键反应。如果动物作出正确选择按红色光下的反应键,则给少量桔子汁作奖励。共记录了155个前额皮层单位。其中40个单位的放电频率在动物完成视觉延缓分辨作业过程中没有明显变化,另外115个单位与该任务的某些时期有关。大多数单位(n=99)在反应键推出时,或者在按反应键的前后有放电频率变化。这99个单位中,15个在暗示期和反应期内放电活动有变化(CR 型单位),13个在延缓期和反应期内放电活动有变化(DR 型单位),42个只在反应期内或反应期后放电频率出现变化(R 型单位),其余29个单位则在分辨任务的各个时期都显示出放电活动变化(CDR 型单位)。上述这些单位中,有少数单位在动物作出正确反应时的放电型式与动物作出错误反应时的放电型式有明显不同。此外,即使动物对任务测试不作出按键反应时,也观察到16个单位的放电活动在任

PREFRONTAL UNIT ACTIVITY AND DELAYED COLOR DISCRIMINATION IN MONKEYS

Single unit activities of the dorsolateral prefrontal cortex of the rhesus mon-key were studied during the performance of color discrimination with delay.Thesequence of events of the task is as follows:(1)a cue period of presentation of redand green lights projected respectively on the left and the right display windowsfor 1.2 seconds,(2)a delay period of 2-4 seconds and(3)a reaction period du-ring which the animal should select to press one of the two keys under each windowafter the keys were automatically protruded out and a small amount of orangejuice would be given as a reward when the animal pressed the right key.A total of 155 units were obtained from 3 monkeys and 115 of which were relatedto some events of the task.The majority of the units(n=99)showed changes in dis-charge rate either at the appearance of keys or before and/or after the key waspressed.Among these units,15 changed their discharge rate during the cue andthe reaction periods,13 during the delay and the reaction periods,42 only duringor after the reaction period and 29 during all periods of the task.In addition,16units showed some changes in discharge rate even when the animal did not pressthe key.The results suggest that prefrontal neurons may be involved in the performanceof the delayed visual discrimination task.It is considered that some prefrontalneurons might be related to processing of the visual information,others to the reac-tion of pressing the key and even to some psychophysiological activities after theanimal had made a correct choice of the behaviour to be rewarded.